Turbine wheel of turbocharger

ABSTRACT

A hot wheel of a turbocharger formed by precision casting, including a shaft-shaped hub part disposed at a radially central portion thereof; a plurality of vane parts formed on a periphery of the hub part; an wrench boss formed at a top end of the hub part; and a boss portion formed at a bottom end of the hub part. In the hot wheel having the above-described construction, with an outer configuration of a necessary portion of each of the hub part, the wrench boss, and the boss portion maintained, a cavity open outward is formed at a radially central portion of the hub part with the cavity symmetrically penetrated through the wrench boss.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a turbine wheel of a turbocharger. Moreparticularly, the present invention relates to a turbine wheel for usein a high-temperature gas (hereinafter referred to as a hot wheel),which is manufactured by precision casting process. The presentinvention is intended to decrease the amount of wax in manufacturing thehot wheel model and decrease the weight of the hot wheel to improve therotation response thereof.

2. Description of the Related Art

FIG. 10 is a vertical sectional view showing an example of a hot wheelformed by precision casting. The hot wheel is symmetrical with respectto an axis X thereof. A solid shaft-shaped hub part 1 is disposed at thecenter of the hot wheel. A vane part 2 is circumferentially formed at aplurality of positions of a peripheral surface 11 of the hub part 1which draws a gentle curved surface in the shape of the foot of amountain. The top portion of the hub part 1 is stepped to form an wrenchboss 3 having a diameter smaller than the lower portion. The wrench boss3 has a plurality of approximately triangular concavities andconvexities alternately formed on a peripheral surface 31 thereof. Aboss portion 4 having an annular wall 41 projected downward is formed atthe center of a lower surface 121 of a base portion 12 of the hub part 1which extends outwardly circularly in a plan view. One end of a shaft SHhaving a small diameter is inserted into an inner space of the annularwall 41. An end surface 411 of the annular wall 41 is welded to an endsurface of the shaft SH having a large diameter. Because aheat-resistant alloy such as Inconel composing the hot wheel has a largedensity, the hotwheel is heavy and has a low rotation response.

To overcome this problem, in the hot wheel disclosed in Japanese PatentApplication Laid-Open publication No. 9-53595, the central portionthereof is formed from a heat-resistant aluminum alloy by forging it,whereas the projected portion thereof is formed from a high-strengthheat-resistant alloy by using a liquid quenching method. The centralportion and the projected portion are joined with each other bydiffusion bonding to make the hotwheel lightweight.

But the hot wheel described in the aforesaid publication has a problemthat it has a complicated construction and thus much time and labor arerequired to manufacture it.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above-describedproblems. Therefore it is an object of the present invention to providea hot wheel, of a turbocharger, which can be easily manufactured byprecision casting, has an improved rotation response by making itlightweight, and uses a decreased amount of wax when it is manufactured.

To solve the above-described problems, the present invention provides ahot wheel of a turbocharger formed by precision casting, including ashaft-shaped hub part disposed at a radially central portion thereof; aplurality of vane parts formed on a periphery of said hub part; anwrench boss formed at a top end of said hub part; and a boss portionformed at a bottom end of said hub part. In the hot wheel having theabove-described construction, with an outer configuration of a necessaryportion of each of the hub part, the wrench boss, and the boss portionmaintained, a cavity open outward is formed symmetrically with respectto an axis of the hub part at at least one of the hub part, the wrenchboss, and the boss portion. It is advantageous to form the cavities atthe central portion of the hub part in terms of the strength of the hotwheel.

In the present invention, with the outer configuration of the necessaryportion of each of said hub part, said wrench boss, and said bossportion secured, the cavity open outward is formed symmetrically withrespect to the axis of said hub part at at least one of said hub part,said wrench boss, and said boss portion. Therefore it is possible tomanufacture the hot wheel easily by precision casting and improve theresponse capability thereof by making the hot wheel more lightweightthan the conventional hot wheel with hardly deteriorating the strengththereof. Further the volume of the solid portion of the hot wheel isdecreased owing to the formation of the cavity inside the hot wheel.Therefore it is possible to decrease the amount of wax which is used inmanufacturing the hot wheel model and also decrease the amount of ametal material to be cast. Therefore it is possible to manufacture thehot wheel at a low cost. Furthermore because the entire hot wheel islightweight, it is easy to adjust the rotation balance by grinding thewrench boss in a small amount.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical sectional view showing a hot wheel of a firstembodiment of the present invention.

FIG. 2 is a vertical sectional view showing a hot wheel of a secondembodiment of the present invention.

FIG. 3 is a vertical sectional view showing a hot wheel of a thirdembodiment of the present invention.

FIG. 4 is a vertical sectional view showing a hot wheel of a fourthembodiment of the present invention.

FIG. 5 is a vertical sectional view showing a hot wheel of a fifthembodiment of the present invention.

FIG. 6 is a vertical sectional view showing a hot wheel of a sixthembodiment of the present invention.

FIG. 7 is a vertical sectional view showing a hot wheel of a seventhembodiment of the present invention.

FIG. 8 is a vertical sectional view showing a hot wheel of an eighthembodiment of the present invention.

FIG. 9 is a vertical sectional view showing a hot wheel of a ninthembodiment of the present invention.

FIG. 10 is a vertical sectional view showing a conventional hot wheel.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The hot wheel of each of the first through ninth embodiments of thepresent invention is made of a heat-resistant alloy such as Inconel byprecision casting process. The same parts of the hot wheels of theembodiments as those of the above-described conventional hot wheel aredenoted by the same reference numerals as those of the conventional hotwheel. The configurations of the following portions are the same asthose of the conventional hot wheel: a necessary portion of a hub part1, namely, a peripheral surface 11 thereof drawing a gentle curvedsurface in the shape of the base of a mountain, a necessary portion ofan wrench boss 3, namely, a peripheral surface 31 thereof having aplurality of approximately triangular concavities and convexities formedthereon, and a necessary portion of a boss portion 4, namely, an endsurface 411 of an annular wall 41 thereof. A vane part 2 is identical tothat of the conventional hot wheel.

First Embodiment

In the first embodiment of the present invention, as shown in FIG. 1, acavity S is formed at the radially central portion of the hub part 1 ofthe hot wheel with the cavity S1 extended in the longitudinal directionthereof. The cavity S1 is symmetrical with respect to an axis X of thehub part 1 and cross sectionally circular. The cavity S1 penetratesthrough the wrench boss 3 and is open at an upper portion thereof. Alower end of the cavity S1 reaches a partitioning wall 13 disposed atthe boundary area to the boss portion 4. This construction makes the hotwheel more lightweight by about 20% than the conventional hot wheel withhardly deteriorating the strength thereof.

Second Embodiment

In the second embodiment of the present invention, as shown in FIG. 2,the partitioning wall 13 (see FIG. 1) of the first embodiment iseliminated to open a lower portion of the cavity S1 into the bossportion 4. This construction makes the hot wheel more lightweight byabout 1% than the hot wheel of the first embodiment.

Third Embodiment

In the third embodiment of the present invention, as shown in FIG. 3,the configuration of the peripheral surface 11 of the hub part 1 is thesame as that of the conventional hot wheel. A peripheral portion, of thebottom surface of the base portion 12 of the hub part 1, adjacent to theboss portion 4 is scooped deeply annularly and symmetrically withrespect to the axis X of the hot wheel to form a cavity S2 which isapproximately triangular in section and open downward. The peripheralsurface of the cavity S2 is curved along the curved peripheral surface11 of the hub part 1 to allow an outer wall 111 to have a predeterminedthickness on the periphery of the base portion 12 of the hub part 1.This construction makes the hot wheel more lightweight by about 25% thanthe conventional hot wheel with hardly deteriorating the strengththereof.

Fourth Embodiment

In the fourth embodiment of the present invention, as shown in FIG. 4, acavity S3 is formed at the radially central portion of the hub part 1 ofthe hot wheel with the cavity S3 extended in the longitudinal directionthereof. The cavity S3 is symmetrical with respect to the axis X of thehub part 1 and cross sectionally circular. The diameter of a circle ofthe cavity S3 becomes gradually larger downward along the curvedperipheral surface 11 of the hub part 1. The cavity S3 penetratesthrough the wrench boss 3 and is open at an upper face thereof. A lowerend of the cavity S3 reaches the partitioning wall 13 disposed at theboundry area to the boss portion 4. The peripheral surface of the cavityS3 is curved along the curved peripheral surface 11 of the hub part 1 toallow an outer wall 112 to have a predetermined thickness on theperiphery of the wrench boss 3 and that of the hub part 1. Thisconstruction makes the hot wheel more lightweight by about 35% than theconventional hot wheel with hardly deteriorating the strength thereof.

Fifth Embodiment

In the fifth embodiment of the present invention, as shown in FIG. 5, acavity S4 is formed at the radially central portion of the hub part 1 ofthe hot wheel with the cavity S4 extended in the longitudinal directionthereof. The cavity S4 is symmetrical with respect to the axis X of thehub part 1 and cross sectionally circular. An upper end of the cavity S4reaches a partitioning wall 14 disposed at the boundary area to thewrench boss 3. A lower portion of the cavity S4 is open into the bossportion 4. As in the case of the third embodiment, the cavity S2 (seeFIG. 3) is formed on the peripheral portion, of the bottom surface ofthe base portion 12 of the hub part 1, adjacent to the boss portion 4.This construction makes the hotwheel more lightweight by about 40% thanthe conventional hot wheel with hardly deteriorating the strengththereof.

Sixth Embodiment

In the sixth embodiment of the present invention, as shown in FIG. 6, acavity S1 (see FIG. 1) is formed at the radially central portion of thehub part 1 of the hot wheel with the cavity S1 extended in thelongitudinal direction thereof and reaches the partitioning wall 13. Asin the case of the third embodiment, the cavity S2 (see FIG. 3) isformed on the peripheral portion, of the bottom surface of the baseportion 12 of the hub part 1, adjacent to the boss portion 4. Thisconstruction makes the hot wheel more lightweight by about 43% than theconventional hot wheel with hardly deteriorating the strength thereof.

Seventh Embodiment

In the seventh embodiment of the present invention, as shown in FIG. 7,the partitioning wall 13 (see FIG. 6) of the sixth embodiment iseliminated to open a lower portion of the cavity S1 into the bossportion 4. This construction makes the hot wheel more lightweight byabout 1% than the hot wheel of the sixth embodiment.

Eighth Embodiment

In the eighth embodiment of the present invention, as shown in FIG. 8,the central portion of the hub part 1 of the hot wheel is solid. Aregion from the peripheral portion, of the bottom surface of the baseportion 12 of the hub part 1, adjacent to the boss portion 4 to theperipheral portion of the main body of the hub part 1 is scooped deeplyannularly and symmetrically with respect to the axis X of the hotwheelto form a cavity S5 open downward, with the peripheral surface 11 of thehub part 1 curved similarly to the conventional hot wheel. Theperipheral surface of the cavity S5 is curved along the curvedperipheral surface 11 of the hub part 1 to allow an outer wall 113 tohave a predetermined thickness on the periphery of the hub part 1. Thisconstruction makes the hot wheel more lightweight by about 50% than theconventional hot wheel with hardly deteriorating the strength thereof.

Ninth Embodiment

In the ninth embodiment of the present invention, as shown in FIG. 9, acavity S6 is formed at the radially central portion of the hub part 1with the cavity S6 extended in the longitudinal direction thereof. Thecavity S6 is symmetrical with respect to an axis X of the hub part 1 andcross sectionally circular. The diameter of a circle of the cavity S6becomes gradually larger downward along the curved peripheral surface 11of the hub part 1. As the base portion 12 becomes larger outward, thediameter of the cavity S6 becomes increasingly large outward and maximumat a portion of the base portion 12. A lower end of the cavity S6 isopen into the boss portion 4 with an annular wall 41 formed similarly tothe conventional hot wheel. In the construction of the hot wheel of theninth embodiment, an outer wall 114 having a predetermined thickness isformed along the curved peripheral surface of the hot wheel symmetricalwith respect to the axis thereof. Therefore it is possible to prevent astress from concentrating at a portion of the hot wheel and decrease theweight thereof by about 20% than the conventional hot wheel with hardlydeteriorating the strength thereof.

1. A turbine wheel of a turbocharger formed by precision casting,comprising: a shaft-shaped hub part disposed at a radially centralportion thereof; a plurality of vane parts formed on a periphery of saidhub part; an wrench boss formed at a top end of said hub part; and aboss portion formed at a bottom end of said hub part, wherein with anouter configuration of a necessary portion of each of said hub part,said wrench boss, and said boss portion maintained, a cavity openoutward is formed symmetrically with respect to an axis of said hub partat at least one of said hub part, said wrench boss, and said bossportion.
 2. A turbine wheel of a turbocharger according to claim 1,wherein said cavity is formed at a radially central portion of said hubpart.
 3. A turbine wheel of a turbocharger according to claim 2, whereinsaid cavity is symmetrical with respect to said axis of said hub partand cross sectionally circular; and a diameter of a circle of saidcavity becomes gradually larger downward along a curved peripheralsurface of said hub part.
 4. A turbine wheel of a turbocharger accordingto claim 2, wherein said cavity penetrates through an wrench boss and isopen outward.
 5. A turbine wheel of a turbocharger according to claim 2,wherein said cavity is open into said boss portion.
 6. A turbine wheelof a turbocharger according to claim 1, wherein said cavity is formed ata radially central portion of said hub part; said cavity penetratesthrough an wrench boss and is open outward; and said cavity is open intosaid boss portion.
 7. A turbine wheel of a turbocharger according toclaim 6, wherein said cavity is symmetrical with respect to said axis ofsaid hub part and cross sectionally circular; and a diameter of a circleof said cavity becomes gradually larger downward along a curvedperipheral surface of said hub part.
 8. A turbine wheel of aturbocharger according to claim 1, wherein a peripheral portion, of abottom surface of a base portion of said hub part, adjacent to said bossportion disposed on a lower surface of said proximal portion of said hubpart is scooped annularly and symmetrically with respect to said axis ofsaid hub part to form said cavity.
 9. A turbine wheel of a turbochargeraccording to claim 8, wherein said cavity is reached to a peripheralportion of a main body of said hub part.
 10. A turbine wheel of aturbocharger according to claim 3, wherein said cavity penetratesthrough an wrench boss and is open outward.
 11. A turbine wheel of aturbocharger according to claim 3, wherein said cavity is open into saidboss portion.